[3] Early in his life he converted to Roman Catholicism, and as the associate of George Gordon, 1st Marquess of Huntly joined in the Spanish conspiracies against the throne of Queen Elizabeth.

[5] He engaged with Huntly and Crawford in a rebellion in the north of Scotland, but their forces surrendered at Aberdeen on the arrival of the king in April; and in July, Erroll gave himself up to James, who leniently refrained from exacting any penalty.

On 21 April 1590 the Earl of Montrose and others at Megginch Castle tried to persuade him not to marry her, but Erroll argued he could change his wife's friends' alliances.

[8] Erroll was imprisoned on suspicion of complicity in the attempt made by Francis Stewart, 5th Earl of Bothwell and Patrick Gray, 6th Lord Gray to surprise the king at Falkland in June 1592; and though he obtained his release, he was again proclaimed a rebel on account of the discovery of his signature to two of the Spanish Blanks, unwritten sheets subscribed with the names of the chief conspirators in a plot for a Spanish invasion of Scotland, to be filled up later with the terms of the projected treaty.

After a failure to apprehend him in March 1593, Erroll and his companions were sentenced to abjure Roman Catholicism or leave the kingdom; and on their non-compliance were in 1594 declared traitors.

The rebel lords left Scotland in 1595, and Erroll, on report of his further conspiracies abroad, was arrested by the states of Zeeland, but was afterwards allowed to escape.

[4] A letter from the Privy Council about a pension paid to the Earl of Erroll in January mentions that one of his daughters served Anne of Denmark.

The reality of his conversion was disputed, and on 21 May 1608 he was confined to the city of Perth for the better resolution of his doubts, being subsequently declared an obstinate "papist", excommunicated, deprived of his estate, and imprisoned at Dumbarton; and after some further vacillation was finally released in May 1611.